Question : The probability that a random chosen three-digit number has exactly 3 factors is
(A) 2/225
(B) 7/900
(C) 1/800
(D) none of these
Answer : option (B)
Solution :
A number has exactly 3 factors if the number is squares of a prime number. Squares of 11, 13, 17,
19, 23, 39, 31 are 3-digit numbers. Hence, the required probability is 7/900